My experience with laptops is that they go into sleep or hibernate if you close the lid. You might be able to change that behavior in some Control Panel option, but that most likely is maker or model or Windows version dependent. Maybe under the Energy saving options (I don't have your Vostro 1220 to check, but you won't find it difficult to look for yourself).
But a very useful workaround I use myself is to close it not fully, but nearly. Just stick something (a ballpoint or something a little bit thicker) between the lid and the base of the laptop, so it doesn't think it's closed.
Kees
I want to use my Vostro 1220 with a KVM box

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